JP6236809B2 - Electrophotographic photosensitive member and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member in which an intermediate layer and a photosensitive layer are provided on a conductive support, and an image forming apparatus and a process cartridge using the same, and more particularly, in an environment of low temperature and low humidity to high temperature and high humidity. The present invention relates to an electrophotographic photosensitive member that undergoes little change in characteristics upon repeated use, and that causes little increase in residual potential and black spot image, and an image forming apparatus and process cartridge using the same.

Electrophotographic image forming apparatuses are used in fields such as copying machines and laser beam printers because of their high speed and high print quality.
As a photoconductor used in an electrophotographic image forming apparatus, development of an organic photoconductor (OPC) using an organic photoconductive material has been promoted and has been gradually spread.
Also, the structure of the photoconductor is changed from a single layer type photoconductor in which a charge transfer complex or charge generation material is dispersed in a binder resin to a function separation type photoconductor in which the charge generation layer and the charge transport layer are separated. The performance has also improved.
In addition, as a constituent layer of the photoconductor, the photoconductive layer is improved in adhesion, improved coatability of the photoconductive layer, improved chargeability, prevention of unnecessary charge injection from the support, and defect coating on the support. A layer is also provided.
For example, currently, in the function-separated type photoconductor, a structure in which an intermediate layer is first formed on a conductive support and a charge generation layer and a charge transport layer are formed on the intermediate layer is mainly used. Conventionally, as the resin used for the intermediate layer, for example, water-soluble resins such as polyvinyl alcohol and casein, alcohol-soluble resins such as nylon resins, polyurethane, melamine resins, phenol resins, alkyd resins, epoxy resins, and siloxane resins Etc. are known.
Furthermore, the resin is cured with heat to form a three-dimensional network structure to improve the solvent resistance.

Among them, resins such as melamine resin, alkyd / melamine resin, acrylic / melamine resin, phenol resin, and copolymerized polyamide are used because they have excellent coating solution stability. Further, a photoreceptor in which a metal oxide that is an inorganic pigment is dispersed in a resin of an intermediate layer has been proposed. If there is specular reflection on the surface of the intermediate layer when writing coherent light, the specularly reflected light interferes, and the density unevenness of the interference fringe pattern occurs in the image.
However, by including a metal oxide as a white pigment in the intermediate layer, regular reflection on the surface of the intermediate layer can be prevented and generation of interference fringes can be suppressed.
Further, when a charge is applied to the surface of the photoreceptor in the charging step, a reverse charge is induced on the support side.
In this case, if the electric resistance of the intermediate layer is too low, the intermediate layer cannot block the charge injection from the support to the photosensitive layer, and the portion where the charge injection from the support to the photosensitive layer occurs is insufficiently charged. It becomes an image defect like a black spot.

On the other hand, if the resistance of the intermediate layer is too high, of the positive and negative charges generated in the charge generation layer during exposure, the charge that should escape to the support side is blocked by the intermediate layer, and the residual potential increases on the surface of the intermediate layer. .
Therefore, a metal oxide, which is a conductor, is added to a resin that is relatively difficult to conduct electricity, and the electric resistance is adjusted by adjusting the addition ratio or by adjusting the film thickness, thereby injecting charge from the support to the photosensitive layer. Although the suppression and the increase in the residual potential are suppressed to some extent, there is a limit to improvement only by this countermeasure method.
Also, when the photoreceptor is used repeatedly, the surface potential of the photoreceptor does not rise immediately even if the charge is applied to the photoreceptor due to charges trapped in the intermediate layer in the charging step, and the amount of charge on the photoreceptor is not increased. After the flow, a charge rising delay that normal charging starts is generated.
When an image is formed using a photoconductor having a delay in charge rising, even if the charging process is performed under conditions that should originally provide a sufficient charging potential, a desired surface potential cannot be obtained before image exposure. Density unevenness occurs.

In the case of an intermediate layer containing a metal oxide, in order to prevent abnormal images such as the above-mentioned stability of electrical characteristics and black spots, the metal oxide contained or the surface of the metal oxide is selected. Processing is performed or various additives are added to the intermediate layer.
For example, by including a metal oxide whose surface is treated with an organosilicon compound in the intermediate layer, a method for suppressing the increase in the residual potential of the photoconductor, a method for suppressing the occurrence of a black spot image, or an increase in the residual potential And a technique for suppressing both black spot image generation have been proposed (see, for example, Patent Documents 1 to 3).

  In addition, the intermediate layer containing a coupling agent having an unsaturated bond, a metal oxide, and a binder suppresses an increase in the residual potential of the photoreceptor and improves the storage stability of the coating solution. (See, for example, Patent Document 4).

Alternatively, there is a technique for improving the electrical characteristics and image characteristics of an electrophotographic photosensitive member in a wide range of environments ranging from high temperature and high humidity to low temperature and low humidity by using an intermediate layer containing polyol-coated titanium oxide particles and a binder resin. It has been proposed (for example, see Patent Document 5).
Further, there has been proposed a technique for reducing environmental stability and image defects by containing 20% by mass or more of zirconium oxide in the intermediate layer (see, for example, Patent Document 6).

  Proposed for a method that contains a white metal oxide or metal fluoride in the intermediate layer and polyalkylene glycol in the charge generation layer or intermediate layer, so that the residual potential is small and the charge rise delay due to fatigue does not occur. (For example, see Patent Document 7).

  However, even if these methods are used, even if the residual potential rise and black spot image can be suppressed, there is no charge rise delay due to repeated use of the photoconductor, and there is no residual charge rise and black spot image. There was no way to reduce it. In particular, it has been difficult to reduce black spot images in a high temperature and high humidity environment, and to suppress an increase in residual potential in a low temperature and low humidity environment.

  The present invention has been made in view of the above-described problems of the prior art, and in an electrophotographic photosensitive member in which an intermediate layer and a photosensitive layer are sequentially provided on a conductive support, there is little change in characteristics even during repeated use. Also provided is an electrophotographic photosensitive member that has little residual potential increase in a low-temperature and low-humidity environment and little black spot image generation under a high-temperature and high-humidity environment, and an electrophotographic image forming apparatus and process using this electrophotographic photosensitive member An object is to provide a cartridge.

As a result of intensive studies to solve the above-mentioned problems, the present inventors used at least a titanium oxide as an inorganic pigment surface-treated with aluminum hydroxide for an intermediate layer, and used a water absorption ratio ([30 ° C., relative Maintaining the water absorption (g)] / [specific surface area of inorganic pigment (m ² )] when left in an environment of 90% humidity for 1 hour within an appropriate range, the content of titanium oxide is within an appropriate range In addition, the volume ratio of the inorganic pigment in the intermediate layer is kept in an appropriate range, and the volume resistivity of the intermediate layer is kept in an appropriate range so that there is little change in characteristics due to repeated use of the photoreceptor, and low temperature and low humidity. It has been found that an electrophotographic photosensitive member can be provided in which the residual potential rises at low temperature and the occurrence of black spot images under high temperature and high humidity is low.
When the water absorption is 0.01 or more, the volume resistance of the intermediate layer is remarkably lowered with water absorption of the inorganic pigment in a high temperature and high humidity environment, and black spots occur in the image. When the content of titanium oxide in the inorganic pigment is 70% by weight or less, the residual potential is increased by repeated use due to the influence of impurities. When the content is 95% by weight or more, the volume resistivity in the intermediate layer is remarkably lowered, and repeated use. As a result, the image quality deteriorates and black spots and fogging occur. In addition, when the volume resistance of the intermediate layer at an electric field strength of 2.5 × 10 ⁵ V / cm is 5 × 10 ¹¹ Ωcm or less, black spots or ground fog occurs due to an abnormal current from the substrate, and at 1 × 10 ¹³ Ωcm or more. Sensitivity decreases and residual potential increases.
Thus, the above problems are solved by the present invention described in the following (1) to (5).
(1) In a photoreceptor having an intermediate layer and a photosensitive layer on a conductive support, the intermediate layer contains titanium oxide treated with aluminum hydroxide and a binder resin, and the volume ratio of the inorganic pigment in the intermediate layer Is 30% to 50%, the titanium oxide content in the inorganic pigment is 70% to 95% by weight, and the water absorption ratio ([30 ° C., relative humidity 90%, left in an environment for 1 hour. The water absorption (g)] / [specific surface area of inorganic pigment (m ² )] is 0.01 or less, and the intermediate layer has a volume at an electric field strength of 2.5 × 10 ⁵ V / cm. An electrophotographic photoreceptor having a resistivity of 1.0 × 10 ¹¹ Ωcm or more and 1.0 × 10 ¹³ or less.
(2) The electrophotographic photosensitive member according to (1), wherein the titanium oxide treated with aluminum hydroxide is further treated with siloxane.
(3) The electrophotographic photosensitive member according to (1) or (2), wherein the binder resin is a copolymerized polyamide resin.
(4) In an image forming apparatus having an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a cleaning unit, and a transfer unit, the electrophotographic photosensitive member is any one of (1) to (3). An image forming apparatus characterized by being an electrophotographic photosensitive member.
(5) An electrophotographic photosensitive member and at least one unit selected from a charging unit, an exposure unit, a developing unit, a cleaning unit, and a transfer unit are integrally supported and detachably attached to an electrophotographic image forming apparatus main body. A process cartridge according to claim 1, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of (1) to (3).

  As will be understood from the following detailed and specific description, according to the present invention, there is little delay in charging rise even during repeated use, and the residual potential rise under low temperature and low humidity environment and black under high temperature and high humidity. An extremely excellent effect of providing an electrophotographic photosensitive member with little generation of a spot image, an electrophotographic image forming apparatus using the same, and a process cartridge is exhibited.

It is a schematic sectional drawing which shows the example of 1 structure of the electrophotographic photoreceptor in this invention. It is a schematic sectional drawing which shows another structural example of the electrophotographic photoreceptor in this invention. 1 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus according to the present invention.

The electrophotographic photoreceptor of the present invention will be further described.
Here, FIG. 1 is a schematic cross-sectional view showing one structural example of the electrophotographic photosensitive member in the present invention. In FIG. 1, an intermediate layer 2 and a photosensitive layer 3 are sequentially provided on a conductive support 1. FIG. 2 is a schematic sectional view showing another configuration example of the electrophotographic photosensitive member in the present invention. In the configuration example of FIG. 2, a photosensitive layer 3 comprising an intermediate layer 2, a charge generation layer 3 a mainly composed of a charge generation material and a charge transport layer 3 b mainly composed of a charge transport material on a conductive support 1. Are stacked. 1 to 2 are examples, and the electrophotographic photosensitive member of the present invention is not limited to these configurations.

≪Intermediate layer, materials used≫
[(1); Treatment of titanium oxide fine particles with aluminum hydroxide]
The aluminum hydroxide-treated titanium oxide fine particles used in the present invention can be produced, for example, as follows. For example, rutile-type titanium oxide fine particles having an average primary particle diameter of about 10 nm to 20 nm are dispersed in an aqueous solution of an aluminum salt such as aluminum chloride, and an alkali such as caustic soda is added to the aluminum hydroxide to thereby convert aluminum hydroxide into titanium oxide. It is deposited on the surface of the fine particles. Next, the titanium oxide fine particles are ignited at about 500 ° C. to obtain aluminum hydroxide-treated titanium oxide. In the present invention, the titanium oxide content in the inorganic pigment is preferably set to about 70% to 95%. When the content of titanium oxide in the inorganic pigment is 70% by weight or less, the residual potential is increased by repeated use due to the influence of impurities. When the content is 95% by weight or more, the volume resistivity in the intermediate layer is remarkably lowered. Image quality deteriorates and black spots and fogging occur.
The titanium oxide content in the inorganic pigment can be measured by the method described in JIS K5116.
Although the inorganic pigment of the present invention can be prepared by the above-mentioned method, a preferred product as a commercially available inorganic pigment is TTO-55 (A) manufactured by Ishihara Sangyo. Products with different water absorption ratios include TTO-51 (A) and the like, which are not preferable because they do not fall within the scope of the present invention.
Furthermore, it has been confirmed that the siloxane treatment is effective as a surface treatment in addition to the aluminum hydroxide treatment.

[(2) Water absorption ratio: ([Amount of water absorbed when left for 1 hour in an environment of 30 ° C. and 90% relative humidity (g)] / [Specific surface area of inorganic pigment (m ² )])]
Water absorption (a certain inorganic pigment is allowed to stand in an environment of room temperature 30 ° C. and relative humidity 90% for 1 hour, and its weight (w1) is measured. The inorganic pigment is allowed to stand in a drying oven at 90 ° C. for 1 hour, and its weight (W2) is measured, and w1-w2 is defined as a water absorption amount.
Specific surface area (The specific surface area of the inorganic pigment is determined by adsorption of nitrogen gas by the simple BET method.)
Here, the water absorption ratio is preferably 0.01 or less. When the water absorption ratio is 0.01 or more, the volumetric efficiency of the intermediate layer is reduced due to water absorption of the inorganic pigment contained in the intermediate layer in a high temperature and high humidity environment, and black spots on the image. Fogging occurs.
Such a water absorption rate can be adjusted, for example, by making the raw material liquid fine with a mortar or the like in a state before production.

[(3) Volume resistivity]
For the volume resistivity of the intermediate layer, the intermediate layer was formed on an aluminum substrate using a sheet coater and dried at 100 ° C. for 10 minutes. The intermediate layer thickness was 1 μm. Subsequently, a gold electrode was vapor-deposited on the intermediate layer, and the volume resistivity between the aluminum substrate and the gold electrode was measured with a high resistance meter 4339A manufactured by HP. In the present invention, the volume resistivity of the intermediate layer at an electric field strength of 2.5 × 10 ⁵ V / cm is preferably 1.0 × 10 ¹¹ Ωcm or more and 1.0 × 10 ¹³ Ωcm or less. When it is 1.0 × 10 ¹¹ Ωcm or less, predetermined charging characteristics cannot be obtained, density unevenness and the like are likely to occur, and black spots and fogging occur due to abnormal current from the substrate. If it is 1.0 × 10 ¹³ Ωcm or more, the sensitivity decreases and the residual potential increases.

[(4) Volume ratio of inorganic pigment]
The volume ratio of the inorganic pigment to the binder resin is expressed as a mixed volume ratio converted from the specific gravity of the inorganic pigment and the binder resin. Specifically, the specific gravity of the inorganic pigment having a titanium oxide content of 70% by weight or more is 4.2 g / and cm ^3, the specific gravity of the polyamide resin is calculated using a value obtained by volume in terms of the weight as 1.12 g / cm ^3. When the volume ratio is less than 30%, the properties of the intermediate layer depend on the properties of the binder resin, and the residual potential changes greatly particularly in changes in temperature and humidity and repeated use, and image unevenness is likely to occur. On the other hand, if it is 50% or more, there are many voids in the intermediate layer, for example, the adhesiveness with the charge generation layer is lowered, and if it exceeds 3/1, air is accumulated, which is applied and dried on the photosensitive layer. At times, it causes bubbles and causes coating defects.
Volume ratio calculation method
Inorganic pigment volume Vf calculated from the weight of the inorganic pigment
Resin volume Vr calculated from resin weight
Inorganic pigment ratio = Vf / (Vf + Vr) × 100

  As a binder resin for the intermediate layer, polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid ester, methacrylic acid ester, silicone resin, phenoxy resin, polysulfone resin, polyvinyl butyral resin, polyvinyl formal resin, polyester Examples include resins, cellulose ester resins, cellulose ether resins, urethane resins, phenol resins, epoxy resins, polycarbonate resins, polyarylate resins, polyamide resins, polyimide resins, melamine resins, alkyd resins, and the like. Among the resins, polyamide resin is preferable in terms of increase in residual potential with repeated use, liquid stability for intermediate layer, and film formability, and more preferably 3 types of nylon, 66 nylon, 610 nylon and 12 nylon. Alternatively, four types of copolymerized polyamides are preferred for environmental stability.

The film thickness of the intermediate layer in the present invention is desirably set in the range of 0.1 to 50 μm, and more desirably in the range of 1 to 8 μm.
When the film thickness of the intermediate layer is less than 0.1 μm, the function as the intermediate layer is insufficient and the effect on pre-exposure fatigue is reduced. Conversely, when the film thickness of the intermediate layer exceeds 50 μm, When the smoothness is lost and the thickness exceeds 8 μm, the sensitivity of the photoreceptor is lowered, and even if the effect on the pre-exposure fatigue is maintained, the effect on the environmental fluctuation is lost.

[Support]
As the conductive support used in the electrophotographic photosensitive member of the present invention, a conductive support having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, etc. Metal, tin oxide, indium oxide or other metal oxide coated with film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. After forming a tube by a method such as extrusion or drawing, a tube subjected to surface treatment such as cutting, superfinishing or polishing can be used.
Further, endless nickel belts and endless stainless steel belts disclosed in JP-A-52-36016 can also be used as the conductive support.
In addition, those obtained by dispersing and coating conductive powder in an appropriate binder resin on the support can also be used as the conductive support of the present invention.
Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver, or metal oxide powder such as conductive tin oxide and ITO. It is done.
The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin.
Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.
In addition, heat shrinkage in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, and Teflon (registered trademark) on a suitable cylindrical conductive support. What provided the electroconductive layer with the tube can be used suitably as an electroconductive support body of this invention.

<Photosensitive layer>
[Charge generation layer]
Next, the photosensitive layer constituting the electrophotographic photoreceptor of the present invention will be described.
The photosensitive layer may be a single layer type structure or a function separation type structure in which a charge generation layer and a charge transport layer are laminated. The function separation type structure will be described below as an example.
That is, the charge generation layer is a layer formed mainly of a charge generation material, and a binder resin may be used as necessary.

As the charge generation material, inorganic materials and organic materials can be used. Examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon.
As amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms or phosphorous atoms are preferably used.

On the other hand, a known material can be used as the organic material. For example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, azulenium salt pigments, squaric acid methine pigments, azo pigments having carbazole skeleton, azo pigments having triphenylamine skeleton, azo pigments having diphenylamine skeleton, dibenzothiophene skeleton An azo pigment having a fluorenone skeleton, an azo pigment having an oxadiazole skeleton, an azo pigment having a bis-stilbene skeleton, an azo pigment having a distyryl oxadiazol skeleton, an azo pigment having a distyrylcarbazole skeleton, Perylene pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and azomethine pigments, Jigoido based pigments, and bisbenzimidazole pigments.
These charge generation materials can be used alone or as a mixture of two or more.

  The binder resin used as necessary for the charge generation layer includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N. -Vinyl carbazole, polyacrylamide, etc. are mentioned. These binder resins can be used alone or as a mixture of two or more. Moreover, you may add a low molecular charge transport material as needed.

  Charge transport materials that can be used in the charge generation layer include electron transport materials and hole transport materials. Examples of the electron transport material include chloroanil, bromanyl, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7- Examples thereof include electron accepting substances such as trinitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.

  Examples of the hole transporting material include the following electron donating materials and are used favorably. For example, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline , Phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, thiophene derivatives, and the like. These hole transport materials can be used alone or as a mixture of two or more.

The charge generation layer is mainly composed of a charge generation material, a solvent, and a binder resin, and any additive such as a sensitizer, a dispersant, a surfactant, or silicone oil may be contained therein. Good.
The method for forming the charge generation layer can be roughly classified into a vacuum thin film preparation method and a casting method from a solution dispersion system.
As the former method, a vacuum deposition method, a glow discharge decomposition method, an ion plating method, a sputtering method, a reactive sputtering method, a CVD method, or the like is used, and it is well formed using the inorganic material and the organic material described above. can do.
Further, in order to provide the charge generation layer by the casting method, a ball mill, an attritor or the like using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, or butanone together with the above-described inorganic or organic charge generation material if necessary. It can be formed by dispersing with a sand mill or the like, and applying the solution after diluting the dispersion appropriately.
The coating can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.
The thickness of the charge generation layer provided as described above is suitably about 0.01 to 5 μm, preferably 0.05 to 2 μm.

[Charge transport layer]
On the other hand, the charge transport layer can be formed by dissolving or dispersing a mixture or copolymer mainly composed of a charge transport material and a binder resin component in an appropriate solvent, and applying and drying the mixture. In the invention, examples of the polymer compound that can be used as the binder resin component include polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, polyester, and polyvinyl chloride. , Vinyl chloride / vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluorine resin, epoxy A thermoplastic or thermosetting resin such as a resin, a melamine resin, a urethane resin, a phenol resin, or an alkyd resin may be used, but the present invention is not limited thereto. These polymer compounds can be used singly or as a mixture of two or more kinds, or copolymerized with a charge transport material.

Examples of the material that can be used as the charge transport material include the above-described low molecular weight electron transport materials and hole transport materials.
The usage-amount of a charge transport material is 20-200 mass parts with respect to 100 mass parts of high molecular compounds, Preferably it is about 50-100 mass parts.
Examples of the dispersion solvent that can be used in preparing the charge transport layer coating solution include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone, ethers such as dioxane, tetrahydrofuran, and ethyl cellosolve, toluene, xylene, and the like. Examples include aromatics, halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate.
The thickness of the charge transport layer in the present invention is preferably set in the range of 10 μm to 30 μm, more preferably in the range of 15 μm to 25 μm. The widely used charge transport layer has a film thickness of 25 μm to 30 μm. However, if the film thickness is 25 μm or less, the diffusion of charges during the hole transport process is reduced, so that the resolution is improved. In addition, a normal image can be maintained even when the thickness of the charge transport layer is reduced to 15 μm due to repeated use.

[Image Forming Method, Image Forming Apparatus]
Next, the electrophotographic image forming apparatus of the present invention will be described.
FIG. 3 is a schematic configuration diagram showing an example of an electrophotographic image forming apparatus according to the present invention. As shown in FIG. 3, the electrophotographic image forming apparatus of the present invention comprises an electrophotographic photosensitive member (photosensitive member) 101, a charging means (charging device) 102, an exposure means (image exposure system) 103, a developing means ( A developing device 104 and a transfer means (transfer device) 105 are provided. In this configuration example, a lubricant supply unit 201 that supplies the lubricant 202 to the photoconductor 101 is provided.

When image formation is performed using the above-described electrophotographic image forming apparatus, a voltage of (±) 400 to 1400 V is first applied to the photosensitive member 101 by the charging device (here, a roll-shaped contact charging device) 102, and the photosensitive member. Is charged. After charging (charging) the photosensitive member 101 by charging, a latent image is formed by the image exposure system 103.
An original image is read by a CCD (Charge Coupled Device), and the read original image is converted into a digital signal of LD or LED of 400 to 780 nm and formed on a photoreceptor. By image formation, charge separation is performed in the photosensitive layer, and a latent image is formed on the photoreceptor 101.

  The photoreceptor 101 on which a latent image has been formed according to the document is developed with a developer by the developing device 104, and the document image is visualized (toner image).

  Next, the toner image on the photosensitive member 101 is transferred to a copy sheet 109 fed by the transfer device 105 and then sent to the fixing device 108 to be made into a hard copy.

On the other hand, after the transfer, the remaining toner image is cleaned and cleaned by the cleaning device 106 (consisting of a cleaning brush 106b and an elastic rubber cleaning blade 106a).
Since the latent image (original image) after the toner image is formed is held on the photosensitive member after cleaning, the static eliminator (generally, red light) 107 is used to erase and make uniform. Then, the preparation for the next latent image formation is completed and a series of copying processes is completed.

When the electrophotographic photosensitive member of the present invention is mounted and used in an electrophotographic image forming apparatus, it is less likely to delay charging rise and increase in residual potential even after repeated use, and is formed in a high temperature and high humidity environment. There are few abnormal images such as black spots on the image.
Further, since the electrophotographic photosensitive member is hardly deteriorated even after repeated use, a stable and high-quality image can be obtained over a long period of time in a wide range of environments.
The electrophotographic image forming apparatus as described above may be fixedly incorporated in a copying machine, a facsimile machine, or a printer, but may be incorporated in the apparatus in the form of a process cartridge.

[Process cartridge]
The process cartridge contains an electrophotographic photosensitive member (photosensitive member) and is supported integrally by including at least one means selected from charging means, exposure means, developing means, cleaning means, and transfer means. This is one apparatus (part) that is detachable from the main body of the image forming apparatus. By using a process cartridge, the image forming apparatus can be compactly configured, and simple and steady maintenance work can be performed, and parts can be easily replaced. An excellent image with high quality can be obtained with no increase in residual potential or generation of black spots on the image over a long period of time.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to this. Hereinafter, all “parts” represent “parts by mass”.

[Example 1]
An electrophotographic photosensitive member (photosensitive member) of Example 1 was prepared by sequentially forming an intermediate layer, a charge generating layer, and a charge transporting layer on an aluminum support by the following procedure.

(Formation of intermediate layer)
[Coating liquid for intermediate layer]
The inorganic pigment has a water absorption ratio of 0.003 (the amount of water absorption defined above is 0.135 g, the specific surface area is 45 m ² ), the titanium oxide content in the inorganic pigment is 93%, the inorganic pigment is 9.88 g, and the binder resin. Copolymerized polyamide: Amilan CM8000 (manufactured by Toray) 6.16 g, 70 ml of methanol and 30 ml of propanol as dispersion solvents, 0.6φ: 50 ml of zirconia balls PTZ as dispersion media were placed in a 200 ml mayonnaise bottle and dispersed for 15 hours with a paint shaker Processed. After dispersion, 35 ml of methanol and 15 ml of propanol were added to the container and stirred for about 1 hour, and the dispersion medium was filtered to prepare an intermediate layer coating solution.
This intermediate layer coating solution was applied to an aluminum support having a diameter of 30 mm, a thickness of 0.8 mm and a diameter of 24 mm, and a thickness of 0.8 mm by a dip coating method, followed by drying at 135 ° C. for 20 minutes to obtain an intermediate layer having a thickness of 2 μm. Formed. The inorganic pigment volume ratio of the obtained intermediate layer is
Inorganic pigment volume Vf = 9 · 88 / 4.2 = 2.35
Resin volume Vr = 6.16 / 1.12 = 5.50
Inorganic pigment volume ratio = 2.35 / (2.35 + 5.50) = 30%.
At this time, the volume resistivity of the intermediate layer was 3.5 × 10 ¹¹ Ωcm.

(Generation of charge generator)
The manufacturing method of titanyl phthalocyanine used as a charge generating agent is shown. 29.2 g of 1,3-diiminoisoindoline and 200 ml of sulfolane are mixed, and 20.4 g of titanium tetrabutoxide is added dropwise under a nitrogen stream.
After completion of the dropwise addition, the temperature was gradually raised to 180 ° C., and the reaction was carried out by stirring for 5 hours while maintaining the reaction temperature between 170 ° C. and 180 ° C. After completion of the reaction, the mixture was allowed to cool, and then the precipitate was filtered, washed with chloroform until the powder turned blue, then washed several times with methanol, further washed several times with hot water at 80 ° C., and dried. Crude titanyl phthalocyanine was obtained. Dissolve the crude titanyl phthalocyanine in 20 times the amount of concentrated sulfuric acid, add dropwise to 100 times the amount of ice water with stirring, filter the precipitated crystals, and then repeat washing with water until the washing solution becomes neutral. Got. 2 g of the obtained wet cake was put into 20 g of tetrahydrofuran and stirred for 4 hours. 100 g of methanol was added to this and stirred for 1 hour, followed by filtration and drying to obtain a titanyl phthalocyanine powder of the present invention.
The obtained titanyl phthalocyanine powder was subjected to X-ray diffraction spectrum measurement under the following conditions. As a result, the Bragg angle 2θ with respect to Cu-Kα ray (wavelength 1.542Å) was 27.2 ± 0.2 °, and the maximum peak and minimum angle 7 A titanyl phthalocyanine powder having a peak at .3 ± 0.2 °, no peak in the range of 7.4 to 9.4 °, and no peak at 26.3 ° was obtained.

(Formation of charge generation layer)
15 g of the resulting titanyl phthalocyanine pigment, 8 g of polyvinyl butyral (ESREC BX-1: manufactured by Sekisui Chemical Co., Ltd.) and 500 g of methyl ethyl ketone were prepared by bead milling dispersion so that the average particle size of the pigment was 0.2 μm, and the coating for the charge generation layer The working solution was applied by dip coating.

(Formation of charge transport layer)
Polycarbonate (Iupilon Z200: manufactured by Mitsubishi Gas Chemical Co., Inc.) 10 parts by weight 8 parts of a charge transport material of the following structural formula (1) 80 parts of tetrahydrofuran were dissolved. Subsequently, a charge transport layer coating solution was applied onto the charge generation layer and dried at 125 ° C. for 20 minutes to form a charge transport layer having a thickness of 23 μm, thereby producing an electrophotographic photoreceptor. The film thickness was measured by using an eddy current type contact film thickness meter Fischer scope MMS (manufactured by Fischer Instruments Co., Ltd.) and measuring the film thickness at the drum center position and 6 drum circumferences.

[Example 2]
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the weight of the inorganic pigment for the intermediate layer described in Example 1 was changed to 18.89 g (inorganic pigment volume ratio: 45%). The volume resistivity of the intermediate layer at this time was 1.9 × 10 ¹¹ Ω · cm.

[Example 3]
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the weight of the inorganic pigment for intermediate layer described in Example 1 was changed to 23.11 g (inorganic pigment volume ratio: 50%). The volume resistivity of the intermediate layer at this time was 1.0 × 10 ¹¹ Ω · cm.

[Example 4]
The inorganic pigment for intermediate layer described in Example 2 has a water absorption ratio of 0.002 (the water absorption amount defined above is 0.060 g, the specific surface area is 30 m ² ), and is treated with an aluminum hydroxide surface-treated inorganic pigment ( An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the titanium oxide was changed. The volume resistivity of the intermediate layer at this time was 1.2 × 10 ¹¹ Ω · cm.

[Example 5]
The inorganic pigment for intermediate layer described in Example 2 was treated with an aluminum hydroxide surface-treated inorganic pigment (titanium oxide) having a water absorption ratio of 0.0009 (the water absorption amount defined above is 0.540 g, the specific surface area is 60 m ² ). An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the above was changed. The volume resistivity of the intermediate layer at this time was 3.5 × 10 ¹¹ Ω · cm.

[Example 6]
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the inorganic pigment for intermediate layer described in Example 2 was changed to an inorganic pigment (titanium oxide) having a surface content of 70% treated with aluminum hydroxide. At this time, the volume resistivity of the intermediate layer was 3.0 × 10 ¹¹ Ω · cm.

[Example 7]
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the inorganic pigment for intermediate layer described in Example 2 was replaced with an inorganic pigment (titanium oxide) having a surface content of 95% that was treated with aluminum hydroxide. At this time, the volume resistivity of the intermediate layer was 1.0 × 10 ¹¹ Ω · cm.

[Example 8]
The inorganic pigment in Example 2 has a water absorption ratio of 0.001 (the water absorption amount defined above is 0.040 g, the specific surface area is 40 m ² ), and is treated with aluminum hydroxide and dimethylsilicone surface-treated titanium oxide (Ishihara). An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the content was changed to TTO-55 (S) manufactured by Sangyo Co., Ltd. and the content was changed to 90%. The volume resistivity of the intermediate layer at this time was 7.0 × 10 ¹¹ Ωcm.

[Example 9]
The inorganic pigment in Example 8 has a water absorption ratio of 0.001 (the water absorption amount defined above is 0.040 g, the specific surface area is 40 m ² ), and is treated with an aluminum hydroxide and dimethyl silicone surface-treated inorganic pigment (Ishihara An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the content was changed to industrial titanium oxide, TTO-55 (S), and the content was changed to 70%. The volume resistivity of the intermediate layer at this time was 3.9 × 10 ¹² Ωcm.

[Example 10]
The inorganic pigment in Example 8 is changed to a water absorption ratio of 0.0002 (the water absorption amount defined above is 0.022 g, the specific surface area is 90 m ² , SMT100-SAS manufactured by Titanium Oxide), and An electrophotographic photosensitive member was produced in the same manner as in Example 8 except that the content was 80% and the inorganic pigment volume ratio was 30%. The volume resistivity of the intermediate layer at this time was 9.0 × 10 ¹² Ω · cm.

[Example 11]
In Example 2, the binder resin was changed to copolymer polyamide: Amilan CM8000 (manufactured by Toray), and an alkyd resin (Beckolite M-6401-50 manufactured by Dainippon Ink and Chemicals, Inc.) and a melamine resin (Super Becamine G- 821-60 Dainippon Ink Chemical Co., Ltd.) was mixed at a ratio of 65:35 to 6.16 g, and electrophotographic as in Example 2 except that 70 ml of methanol and 30 ml of propanol were used as 100 ml of methyl ethyl ketone. A photoconductor was produced. At this time, the volume resistivity of the intermediate layer was 5.5 × 10 ¹¹ Ω · cm.

[Comparative Example 1]
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the weight of the inorganic pigment for intermediate layer described in Example 2 was changed to 7.70 g (inorganic pigment volume ratio: 25%). The volume resistivity of the intermediate layer at this time was 5.0 × 10 ¹¹ Ω · cm.

[Comparative Example 2]
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the weight of the inorganic pigment for intermediate layer described in Example 2 was changed to 28.27 g (inorganic pigment volume ratio: 55%). The volume resistivity of the intermediate layer at this time was 8.9 × 10 ¹⁰ Ω · cm.

[Comparative Example 3]
An electrophotographic photosensitive member was manufactured in the same manner as in Example 2 except that the inorganic pigment for intermediate layer described in Example 2 was changed to 60% of the content of the inorganic pigment composed of titanium oxide having a surface treated with aluminum hydroxide. The volume resistivity of the intermediate layer at this time was 8.5 × 10 ¹¹ Ω · cm.

[Comparative Example 4]
An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the inorganic pigment for intermediate layer described in Example 2 was changed to 97% of the inorganic pigment content of titanium oxide having a surface treated with aluminum hydroxide. The volume resistivity of the intermediate layer at this time was 8.5 × 10 ¹¹ Ω · cm.

[Comparative Example 5]
The inorganic pigment for intermediate layer described in Example 2 has a water absorption ratio of 0.014 (the amount of water absorption defined above is 1.120 g, the specific surface area is 80 m ² ), and is treated with aluminum hydroxide surface-treated titanium oxide. An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the inorganic pigment was changed. The volume resistivity of the intermediate layer at this time was 2.0 × 10 ¹² Ω · cm.

[Comparative Example 6]
The inorganic pigment for intermediate layer described in Example 2 has a water absorption ratio of 0.024 (the water absorption amount defined above is 2.040 g, and the specific surface area is 85 m ² ). An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the weight of the inorganic pigment was 9.88 g (inorganic pigment volume ratio: 30%). The volume resistivity of the intermediate layer at this time was 5.0 × 10 ¹² Ω · cm.

[Comparative Example 7]
The inorganic pigment for intermediate layer described in Example 2 has a water absorption ratio of 0.024 (the water absorption amount defined above is 2.040 g, and the specific surface area is 85 m ² ). An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the inorganic pigment was used. The volume resistivity of the intermediate layer at this time was 1.2 × 10 ¹² Ω · cm.

[Comparative Example 8]
The inorganic pigment for intermediate layer described in Example 2 was treated with aluminum hydroxide surface-treated inorganic oxide having a water absorption ratio of 0.024 (water absorption amount defined above is 2.040 g, specific surface area is 85 m ² ). An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the pigment weight was 23.11 g (inorganic pigment volume ratio: 50%). The volume resistivity of the intermediate layer at this time was 6.0 × 10 ¹¹ Ω · cm.

[Comparative Example 9]
The inorganic pigment for intermediate layer described in Example 2 has a water absorption ratio of 0.008 (the water absorption amount defined above is 0.480 g, the specific surface area is 60 m ² ), and is not subjected to an aluminum hydroxide surface treatment. An electrophotographic photosensitive member was produced in the same manner as in Example 2 except that the content was changed to an inorganic pigment made of titanium oxide (titanium oxide manufactured by Ishihara Sangyo Co., Ltd., TTO-55 (N)) and the content was changed to 98%. The volume resistivity of the intermediate layer at this time was 6.0 × 10 ¹⁰ Ω · cm.

[Comparative Example 10]
By changing the intermediate layer inorganic pigment described in Example 2 to CR-EL manufactured by Ishihara Sangyo Co., Ltd., the water absorption ratio is 0.002 (the water absorption amount defined above is 0.008 g, and the specific surface area is 40 m ² ). Thus, an electrophotographic photoreceptor was produced in the same manner as in Example 2 except that the titanium oxide content was changed to an untreated inorganic pigment having a surface content of 99% and not subjected to aluminum hydroxide surface treatment. At this time, the volume resistivity of the intermediate layer was 3.5 × 10 ¹⁰ Ω · cm.

[Comparative Example 11]
By changing the inorganic pigment for intermediate layer described in Example 2 to JMT150-AD manufactured by Teika, the water absorption ratio is 0.028 (the water absorption amount defined above is 2.44 g, and the specific surface area is 800 m ² ). An electrophotographic photoreceptor was produced in the same manner as in Example 2 except that the titanium oxide content was changed to an untreated inorganic pigment that was not subjected to aluminum hydroxide surface treatment with a 90% content of titanium oxide. The volume resistivity of the intermediate layer at this time was 6.0 × 10 ¹⁰ Ω · cm.
These results are shown below as a list of examples / comparative examples.

[Evaluation of electrostatic properties after initial and fatigue tests]
Using an electrophotographic photosensitive member evaluation apparatus (manufactured by Yamanashi Denshi Kogyo Co., Ltd.), the electrophotographic photosensitive members produced in the examples and comparative examples were subjected to a temperature of 23 ° C. and humidity of 50% (N / N), a temperature of 10 ° C. The surface potential of the photosensitive member when a discharge current of 25 μA is applied to the photosensitive member by the scorotron method in an environment of 15% humidity (L / L), a temperature of 30 ° C., and an humidity of 80% (H / H). V0) is measured. Thereafter, the discharge current is adjusted so that the surface potential becomes −700 V, and the exposure energy amount when the surface potential is attenuated to ½ (−350 V) irradiated with a semiconductor laser having a wavelength of 780 nm: half exposure energy amount ( E1 / 2) was measured. Further, the surface potential of the photoreceptor when irradiated with an exposure energy of 1.0 μJ / cm ^{2 was} defined as a residual potential (VL), and was measured at the initial stage and after 1000 cycles of fatigue. As the potential deviation after the fatigue test, (initial potential V0) − (V0 after the fatigue test) = ΔV0, and similarly for VL,
The potential change of (initial potential VL) − (VL after fatigue test) = ΔVL was calculated. Here, ΔV0 and ΔVL are preferably within ± 50 (V).

(Image evaluation)
Installed in an electrophotographic image forming apparatus (image MPC2200, manufactured by Ricoh Co., Ltd.) as shown in FIG. 3, and adjusted so that the charging potential is 800 (-V) and the developing bias is 700 (-V). After that, a white image is printed. Using a digital microscope (Keyence Co., Ltd .: VHX-2000), the printed white image is enlarged for a 1 cm ² area to observe black spots / tilts, and the number of black spots / dirts having a diameter of 30 μm or more is counted. Here, 10 or less black spots / chiles were judged as good (◯), and 11 or more as bad (×).
The results are shown in Tables 2 and 3.

As can be seen from Table 2 and Table 3, in Examples 1 to 11, the water absorption of the inorganic pigment, the content of titanium oxide in the inorganic pigment, the volume ratio of the inorganic pigment in the intermediate layer, and the volume of the intermediate layer Resistivity is within the scope of claims of the present invention, initial electrical characteristics under each environment of N / N, L / L, and H / H, deviation of electrical characteristics after fatigue test, environmental dependence of sensitivity, and image evaluation ( It can be seen that (spot / Chile) is excellent.
In Comparative Example 1, the volume ratio of the inorganic pigment is smaller than the claimed range of the present application, in particular, ΔV0 (L / L) is −52 (V), ΔVL (L / L) is 63 (V), and the deviation in the fatigue test is large. It has become.
In Comparative Example 2, the volume ratio of the inorganic pigment is larger than the range of the present invention, and the volume resistivity is also lower than the claimed range. Although there is no problem in electrical characteristics, image evaluation (black spots / chili) at N / N and L / L is poor.
In Comparative Example 3, the content of titanium oxide in the inorganic pigment is less than the claimed range, and ΔV0 (L / L) is −55 (V), and ΔVL (L / L) is 72 (V). The deviation in the test is large.
In Comparative Example 4, when the content of titanium oxide in the inorganic pigment is higher than the claimed range and the volume resistivity is lower than the range of the present invention, there is no problem in electrical characteristics, but image evaluation (black dot / Chile) is getting worse.
Comparative Examples 5 to 8 are cases where the water absorption is out of the range of the present invention. In any case, there is no problem in electrical characteristics, but the image evaluation (black spot / chile) at L / L is poor.
Comparative Example 9 and Comparative Example 10 are cases where an inorganic pigment not subjected to aluminum hydroxide treatment is used as an inorganic pigment, but the volume resistivity is lower than the claimed range and there is no problem in electrical characteristics, but the image is not affected under any environment. Evaluation (spot / Chile) is getting worse.
Comparative Example 11 is a case where an inorganic pigment surface-treated with octylsilane is used, but when the volume resistivity is lower than the range of the present invention, there is no problem in electrical characteristics as in Comparative Example 9 and Comparative Example 10. The image evaluation (black spots / Chile) is worse even in the environment of.

1 Conductive support
2 Middle layer
3 Photosensitive layer
3a Charge generation layer
3b Charge transport layer
101 Electrophotographic photoreceptor
102 Charging means (charging device)
103 Exposure means (image exposure system)
104 Developing means (developing device)
105 Transfer means (transfer device)
106 Cleaning device
106a Rubber cleaning blade
106b Cleaning brush
108 Fixing device
109 copy paper
201 Lubricant supply means
202 Lubricant

Japanese Patent Laid-Open No. 2003-57862 JP 2003-66636 A JP 2002-196522 A Japanese Patent Laid-Open No. 11-15184 JP-A-10-228125 JP-A-11-202518 JP 05-165241 A

Claims (5)

In an electrophotographic photosensitive member having an intermediate layer, a charge transport layer, and a photosensitive layer having a charge generation layer on a conductive support,
The intermediate layer contains titanium oxide treated with aluminum hydroxide and a binder resin, and a volume content ratio of titanium oxide treated with aluminum hydroxide in the intermediate layer is 40.5 vol% or more and 50 vol% or less. The titanium oxide content in the titanium oxide treated with aluminum hydroxide is 70 wt% or more and 95 wt% or less, and has a water absorption ratio (when left in an environment of [30 ° C., relative humidity 90% for 1 hour] Water absorption (g)] / [specific surface area of inorganic pigment (m ² )] is 0.01 or less, and the intermediate layer has a volume at an electric field strength of 2.5 × 10 ⁵ V / cm. The resistivity is 1.0 × 10 ¹¹ Ωcm or more and 1.0 × 10 ¹³ Ωcm or less,
The electrophotographic photoreceptor, wherein the charge transport layer contains at least a compound of the following structural formula (1).
  2. The electrophotographic photoreceptor according to claim 1, wherein the titanium oxide treated with aluminum hydroxide is further treated with siloxane.   The electrophotographic photosensitive member according to claim 1, wherein the binder resin is a copolymerized polyamide resin.   4. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor is an electrophotographic image forming apparatus having an electrophotographic photoreceptor, a charging unit, an exposing unit, a developing unit, a cleaning unit, and a transfer unit. An image forming apparatus characterized by being a photographic photoreceptor.   In a process cartridge which is integrally supported and includes an electrophotographic photosensitive member and at least one means selected from a charging means, an exposure means, a developing means, a cleaning means and a transfer means, and is detachable from the main body of the image forming apparatus A process cartridge, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 3.